Unzipping dsDNA with a force: scaling theory

A double stranded DNA molecule under the stress of a pulling force acting on the strand terminals exhibits a partially denatured structure or can be completely unzipped depending the magnitude of the pulling force. A scaling argument for relationships amongst basic length scales is presented that takes into account the heterogeneity of the sequence. The result agrees with our numerical simulation data, which provides a critical test of the power laws in the unzipping transition region.